Constitution and microstructures of Fe–Al–M–C (M=Ti, V, Nb, Ta) alloys with carbides and Laves phase

Abstract

Iron aluminides are known for their resistance to high temperature corrosion. There is a need to improve the strength at high temperatures. For this, Fe–Al–M–C (M=Ti, V, Nb, Ta) alloys with strengthening carbides and Laves phase are investigated. The aim of the present study is to characterise the high temperature stability of the strengthening particles. This paper presents results on microstructure and constitution of these alloys. The alloys contain 15 or 26 at.% Al, 2 at.% Ti, V, Nb, or Ta, and 1 at.% C. The alloys are prepared by vacuum induction melting and cast into Cu-moulds. The samples are investigated in the as-cast state and after heat treatment at 1000 °C. Microstructural analysis is performed by light optical microscopy (LOM), scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and X-ray diffraction analysis (XRD). The experimentally determined phase equilibria are compared with thermodynamic calculations using Thermo-Calc.